This invention concerns a motor fuel containing a small amount of a particular Mannich condensation product as an additive to improve certain performance characteristics.
It is known that certain exhaust gas emissions are highest during engine warmup, even for vehicles equipped with emission control devices. To minimize one such emission, i.e. carbon monoxide, it has been found desirable to turn off the choke as soon as possible after the engine is started. To allow early choke turn-off without engine stalling, good fuel evaporation is necessary by the time the choke is turned off. Such good evaporation is achieved by having fuel droplets from the carburetor impinge upon a plate heated by hot exhaust gases. The plate is designed to hold the fuel droplets until evaporation takes place. One difficulty in this method for achieving early fuel evaporation is that the heavy ends of the fuel remaining in contact with the hot surface tend to decompose and form deposits. When sufficient deposists are accumulated, the plate becomes ineffective in vaporizing fuel.
There is a need for an additive to prevent or minimize the formation of deposits on the heated plate, preferably one that will provide more than one performance characterisitc so as to reduce the cost of handling and blending different types of additives. This invention provides such a multifunctional additive, one which provides the desired performance characteristics at low costs.
It has now been found that gasolines having incorporated therein small amounts of the reaction product of an alkyl-substituted phenol, a polyamine and formaldehyde exhibit excellent carburetor detergency, antirust protection, antiicing protection and control of deposits in quick-heat intake manifolds.